The invention relates to a shifting point display in a motor vehicle having a manual transmission for providing shifting advice.
In contrast to automatic transmissions, in which the shifting operation is carried out automatically by stored characteristic upshift and downshift curves, in the case of motor vehicles having manual transmissions, the driver himself is responsible for selecting the gears. In order to make this easier for the driver, various shifting point displays are known, which inform the driver as to when he should shift in order to drive, for example, in a particularly efficient fuel consumption manner.
Thus, from German patent document DE 199 63 156 B4, an indicating instrument for a motor vehicle is known to have a display, in which case, as a function of the momentary accelerator pedal position or manual drive position, at least one characteristic engine curve stored in an electric memory is displayed. By means of this representation, the driver is supposed to recognize whether the operating point of his engine is in an optimal range and how the operating range changes when he, for example, no longer provides fuel or changes the gear. In this type of representation, the driver's attention could be excessively diverted from the driving situation because he constantly has to check, by way of the display, whether he is operating the motor vehicle in an optimal operating range.
From German patent document DE 39 12 359 A1, a shift assist advice device is known, which emits shift recommendations for a fuel-consumption-optimized and/or exhaust-pollution-minimized driving method on the basis of detected current conditions of the rotational engine speed, the driving speed, the engaged gear, the accelerator pedal position, and on the basis of engine and transmission characteristics data. This determination of the shift recommendation requires high computing capacities. Another problem occurs when the vehicle is operated in such a manner that the computed optimal gear changes constantly between the currently engaged gear and another gear. The shift advice would then toggle; that is, it would constantly change between active and inactive, which would have a disturbing effect on the driver, or may even put the driver into a state of uncertainty.
There is therefore needed an improved shifting point display, which requires no unnecessary computing capacities and does not put the driver into a state of uncertainty or disturb the driver.
This, and other, needs are met according to the invention by a shifting point display for providing shifting advice in a motor vehicle having a manual transmission and a control unit, the control unit continuously determining a current operating point of the motor vehicle. At least one characteristic upshift indication curve is stored in an electronic memory and an upshift indication is displayed when the current operating point reaches the characteristic upshift indication curve and a lower gear is currently engaged gear. The upshift is displayed until the driver has carried out an upshift operation or until the current operating point reaches and/or falls below a characteristic upshift indication hysteresis curve that is smaller than the characteristic upshift indication curve.
A second shifting point display for providing shifting advice according to the invention in a motor vehicle having a manual transmission and having a control unit for the continuous determination of a current operating point of the motor vehicle is characterized in that at least one characteristic downshift indication curve is stored in an electronic memory and a downshift is indicated when the current operating point reaches the characteristic downshift indication curve and a higher gear is currently engaged. The downshift indication is displayed until the driver has carried out a downshift operation or until the current operating point reaches and/or exceeds a characteristic downshift indication hysteresis curve that is greater than the characteristic downshift indication curve.
The two shifting point displays according to the invention, are therefore, based on characteristic upshift and downshift curves respectively, as stored in motor vehicles having automatic transmissions and used for the automatic shifting operation. In contrast to the characteristic upshift and downshift curves respectively, which are stored in the motor vehicles having an automatic transmission, the characteristic upshift indication curves and downshift indication curves, respectively, in the case of the invention are displaced relative to the above-mentioned characteristic upshift and downshift curves respectively such that, when the driver receives the shift advice, he still has sufficient time to carry out the shifting operation at the optimal point in time. This time period is taken into account when determining the characteristic upshift indication and downshift indication curves, respectively.
As a result of the output of the shift advice when the characteristic upshift indication or downshift indication curve is reached, only very low computing capacities are required because only a comparison has to be made between the characteristic shift indication curves and the current operating point of the motor vehicle.
Another advantage of the indicating devices according to the invention consists of the display, or of the duration of the display, of the respective shift advice. Since the shift advice is not canceled before the driver either has carried out the corresponding shifting operation or the current operating point of the motor vehicle has fallen below the given characteristic upshift indication hysteresis curve that is smaller than the characteristic upshift indication curve, or the operating point of the motor vehicle has exceeded the given characteristic downshift indication hysteresis curve that is greater than the characteristic downshift indication curve, a toggling of the indication is excluded. The distance between the characteristic upshift indication curve and the characteristic upshift indication hysteresis curve or between the characteristic downshift indication curve and the characteristic downshift indication hysteresis curve should be such that, on the one hand, the toggling can be excluded when the vehicle is operated approximately in one operating point and, on the other hand, the indication is no longer active when a shifting operation according to the indication no longer makes sense or is no longer possible.
The upshift advice and/or the downshift advice may be a visual indication, preferably a display, which reflects the target gear, in the instrument panel of the motor vehicle or in a separate display in the motor vehicle.
Advantageously, the relevant characteristic upshift indication curve and the pertaining characteristic upshift indication hysteresis curve and/or the relevant characteristic downshift indication curve and the pertaining characteristic downshift indication hysteresis curve are stored for all gears in the electronic memory. This means that, for the lowest gear, no characteristic downshift indication and pertaining characteristic downshift indication hysteresis curve and, for the highest gear, no characteristic upshift indication curve and pertaining characteristic upshift indication hysteresis curve are stored in the memory. However, for the gears situated in-between, a characteristic upshift indication curve, a respective characteristic upshift indication hysteresis curve, a characteristic downshift indication curve and a pertaining characteristic downshift indication hysteresis curve should be stored. Thus, the output of shift advice to the driver becomes possible over the entire operating range of the motor vehicle, when it is required.
The current operating point is advantageously determined as a function of the rotational output speed or the motor vehicle speed and the accelerator pedal angle, and the characteristic upshift indication curves and/or characteristic downshift indication curves, as well as the pertaining characteristic upshift indication hysteresis curves and/or characteristic downshift indication hysteresis curves are stored as a function of the rotational output speed or the motor vehicle speed and the accelerator pedal angle. By means of the current rotational output speed or the motor vehicle speed and the current accelerator pedal position, it can therefore be determined whether a given characteristic shift indication curve is to be reached and an output of a shift advice is to take place, or whether—if the shift advice is already active and the driver has not carried out a corresponding shifting operation—the characteristic hysteresis curve pertaining to the characteristic shift indication curve has been reached, not been reached, or exceeded.
The shifting point advice can be displayed either sequentially—thus, upward or downward by only one gear—or over several gears—thus, over several gears deviating from the current gear. If, for example, the 2nd gear is currently engaged, a shift advice into the 6th gear can also be displayed when the rotational speed is high. The displayed maximal gear spread may be separately limited in the upshift and downshift direction. The number of shifting operations can thereby clearly be reduced. However, a downshift advice by more than one gear is not meaningful.
In the case of several stored characteristic upshift indication curves, the upshift advice assigned to the maximum characteristic upshift indication curve reached by the operating point is advantageously displayed. Or, in the case of several characteristic downshift indication curves, downshift advice is displayed that is assigned to the maximum characteristic downshift indication curve reached by the operating point. Thus, the shift point display can also output a shift indication to a gear to be engaged that is not situated directly above or below the current gear.
Advantageously, the determination of the upshift advice and/or of the downshift advice does not take place when predetermined conditions have not been met. This means that the determination of the shifting point display is carried out only under certain conditions. These conditions may, for example, be a certain speed range which should not be exceeded or fallen below, or a predetermined rotational speed gradient that should not be exceeded. As a further condition, the vehicle should not be operated in the reverse gear and the brake should also not be depressed.
If the above-mentioned conditions have been met and a shift indication to be displayed is determined within the scope of the shifting point displays according to the invention, advantageously the upshift indication and/or the downshift indication is suppressed, however, when the motor vehicle is cornering or when the motor vehicle is in a downhill operation. The downhill operation can be determined by means of a traction resistance detecting device. Finally, the output of the shift advice does not take place before a frictional connection exists between the drive unit and the transmission.
The upshift indication is advantageously suppressed when a brake operation exists in the motor vehicle. However, the output of the downshift indication takes place when the brake is operated.
The stored characteristic curves advantageously are fuel consumption-optimal characteristic curves; that is, the characteristic curves are defined on the basis of the fuel consumption. When the driver follows the shifting advice, he can operate the motor vehicle in an extremely consumption-effective manner.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings.